DESCRIPTION: (Applicant's Abstract) The goal of this research application is to develop electrophysiological measures for evaluating the central nervous system (CNS) as it is affected by marihuana. This goal will be pursued by assaying young adults who only occasionally ( 1/month) or chronically ( 3/week) smoke marihuana (low- vs. high-risk subjects), with equal and sufficiently large numbers of both male and female subjects employed for all comparisons. Electroencephalographic (EEG) and event-related brain potential (ERP) paradigms that are sensitive to attention and memory processes will be performed by each subject before and after smoking a placebo or marihuana cigarette on two independent occasions. This approach will optimize CNS electrophysiological differences between occasional (low-risk) and chronic (high-risk) adult marihuana users and produce for the first time a comprehensive assessment of marihuana's effect on CNS function. Because both male and female subjects will be employed in each assessment condition, reliable information on gender differences for marihuana's short- and long-term influence also will be acquired. The most sensitive and effective paradigms will provide reliable neuroelectric signatures that reflect marihuana's cognitive effects.